Cho 6 ∫ 0 f ( x ) dx = 12 . Tính I = 2 ∫ 0 f ( 3x ) dx .
Giải thích
Chọn C
\(I = \int\limits_0^2 {f\left( {3x} \right)dx} \)\( = \frac{1}{3}\int\limits_0^2 {f\left( {3x} \right)d\left( {3x} \right)} \)\( = \frac{1}{3}\int\limits_0^6 {f\left( u \right)du} = \)\( = \frac{1}{3}.12 = 4\).